Lidar systems and methods for focusing on ranges of interest

ABSTRACT

Embodiments discussed herein refer to LiDAR systems to focus on one or more regions of interests within a field of view.

CROSS-REFERENCE TO A RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/685,333, filed Jun. 15, 2018, the disclosure of which is incorporatedby reference in its entirety.

FIELD OF THE INVENTION

The present disclosure relates generally to laser scanning and, moreparticularly, to using a laser scanning system to focus on one or moreranges of interest within a field of view.

BACKGROUND

Systems exist that enable vehicles to be driven semi-autonomously orfully autonomously. Such systems may use one or more range finding,mapping, or object detection systems to provide sensory input to assistin semi-autonomous or fully autonomous vehicle control. Light detectionand ranging (LiDAR) systems, for example, can provide the sensory inputrequired by a semi-autonomous or fully autonomous vehicle. LiDAR systemsuse light pulses to create an image or point cloud of the externalenvironment. Some typical LiDAR systems include a light source, a pulsesteering system, and light detector. The light source generates lightpulses that are directed by the pulse steering system in particulardirections when being transmitted from the LiDAR system. When atransmitted light pulse is scattered by an object, some of the scatteredlight is returned to the LiDAR system as a returned pulse. The lightdetector detects the returned pulse. Using the time it took for thereturned pulse to be detected after the light pulse was transmitted andthe speed of light, the LiDAR system can determine the distance to theobject along the path of the transmitted light pulse. The pulse steeringsystem can direct light pulses along different paths to allow the LiDARsystem to scan the surrounding environment and produce an image or pointcloud. LiDAR systems can also use techniques other than time-of-flightand scanning to measure the surrounding environment

BRIEF SUMMARY

Embodiments discussed herein refer to using LiDAR systems and methods tofocus on one or more regions of interests within a field of view. Aregion of interest may occupy a particular portion of the field of viewthat requires additional data or scanning resolution compared to regionsthat are not of interest. The LiDAR systems and methods discussed hereinare able to adjust one or more factors within each field of viewscanning sequence to increase data collection from the one or moreregions of interest during each scan.

A further understanding of the nature and advantages of the embodimentsdiscussed herein may be realized by reference to the remaining portionsof the specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 illustrate an exemplary LiDAR system using pulse signal tomeasure distances to points in the outside environment.

FIG. 4 depicts a logical block diagram of the exemplary LiDAR system.

FIG. 5 depicts a light source of the exemplary LiDAR system.

FIG. 6 depicts a light detector of the exemplary LiDAR system.

FIG. 7 depicts an embodiment of a signal steering system using a singlelight source and detector.

FIG. 8 depicts an embodiment of a signal steering system using two lightsources and two detectors.

FIG. 9 depicts a portion of the scan pattern generated by the embodimentfrom FIG. 8.

FIG. 10 depicts a portion of the scan pattern according to anotherembodiment.

FIG. 11 depicts a portion of the scan pattern according to yet anotherembodiment.

FIG. 12 shows illustrative field of view of a LiDAR system according toan embodiment.

FIG. 13 shows an illustrative block diagram of LiDAR system according toan embodiment.

FIG. 14 shows an illustrative fiber tip arrangement according to anembodiment.

FIGS. 15A and 15B show multiple mirror alignment arrangement that may beused for ROI and non-ROI embodiments.

FIG. 15C shows an illustrative multiple collimator arrangement that maybe used for ROI and non-ROI embodiments.

FIG. 15D shows an illustrative collimator and lens arrangement accordingto an embodiment.

FIG. 16 shows illustrative scanning resolution using multiple fibertips, a multiple mirror alignment arrangement, or multiple collimatorarrangement according to an embodiment.

FIG. 17A shows another illustrative diagram of vertical resolution usingmultiple fiber tips or a multiple mirror alignment arrangement,according to an embodiment.

FIG. 17B shows an illustrative close-up view of a sparse region withinFIG. 17A and FIG. 17C shows an illustrative close-up view of the denseregion within FIG. 17A, according to various embodiments.

FIG. 18 shows illustrative an FOV with variable sized laser pulsesaccording to an embodiment.

FIGS. 19A-19J show illustrative mirrors according to variousembodiments.

FIG. 20 depicts an alternative system similar to the system as depictedin FIG. 8.

FIG. 21 depicts an alternative system similar to the system as depictedin FIG. 8.

FIG. 22 shows an illustrative polygon according to an embodiment.

FIG. 23 depicts a point map using the polygon of FIG. 22 according to anembodiment.

FIG. 24 shows an illustrative block diagram of a LiDAR system accordingto an embodiment.

FIG. 25A and FIG. 25B show different resolutions of data points beingcaptured from objects.

FIG. 26A shows an illustrative optimized angular resolution in avertical FOV with respect to the ground according to an embodiment.

FIG. 26B shows an illustrative graph of a continuously changing angularvertical resolution as a function of the vertical angle in the FOVaccording to an embodiment.

FIG. 27 shows an illustrative graph of step changing angular verticalresolution as a function of the vertical angle in the FOV according toan embodiment.

FIGS. 28-30 show different illustrative processes for handing ROIsaccording to various embodiments.

DETAILED DESCRIPTION

Illustrative embodiments are now described more fully hereinafter withreference to the accompanying drawings, in which representative examplesare shown. Indeed, the disclosed LiDAR systems and methods may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Like numbers refer to like elementsthroughout.

In the following detailed description, for purposes of explanation,numerous specific details are set forth to provide a thoroughunderstanding of the various embodiments. Those of ordinary skill in theart will realize that these various embodiments are illustrative onlyand are not intended to be limiting in any way. Other embodiments willreadily suggest themselves to such skilled persons having the benefit ofthis disclosure.

In addition, for clarity purposes, not all of the routine features ofthe embodiments described herein are shown or described. One of ordinaryskill in the art would readily appreciate that in the development of anysuch actual embodiment, numerous embodiment-specific decisions may berequired to achieve specific design objectives. These design objectiveswill vary from one embodiment to another and from one developer toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming but would nevertheless be a routineengineering undertaking for those of ordinary skill in the art havingthe benefit of this disclosure.

Some light detection and ranging (LiDAR) systems use a single lightsource to produce one or more light signals of a single wavelength thatscan the surrounding environment. The signals are scanned using steeringsystems that direct the pulses in one or two dimensions to cover an areaof the surrounding environment (the scan area) or the field of view.When these systems use mechanical means to direct the pulses, the systemcomplexity increases because more moving parts are required.

For example, some embodiments of the present technology use one or morelight sources that produce light signals of different wavelengths and/oralong different optical paths. These light sources provide the signalsto a signal steering system at different angles so that the scan areasfor the light signals are different (e.g., if two light sources are usedto create two light signals, the scan area associated with each lightsource is different). This allows for tuning the signals to appropriatetransmit powers and the possibility of having overlapping scan areasthat cover scans of different distances. Longer ranges can be scannedwith signals having higher power and/or slower repetition rate (e.g.,when using pulsed light signals). Shorter ranges can be scanned withsignals having lower power and/or high repetition rate (e.g., when usingpulse light signals) to increase point density.

As another example, some embodiments of the present technology usesignal steering systems with one or more dispersion elements (e.g.,gratings, optical combs, prisms, etc.) to direct pulse signals based onthe wavelength of the pulse. A dispersion element can make fineadjustments to a pulse's optical path, which may be difficult orimpossible with mechanical systems. Additionally, using one or moredispersion elements allows the signal steering system to use fewmechanical components to achieve the desired scanning capabilities. Thisresults in a simpler, more efficient (e.g., lower power) design that ispotentially more reliable (due to few moving components).

Some LiDAR systems use the time-of-flight of light signals (e.g., lightpulses) to determine the distance to objects in the path of the light.For example, with respect to FIG. 1, an exemplary LiDAR system 100includes a laser light source (e.g., a fiber laser), a steering system(e.g., a system of one or more moving mirrors), and a light detector(e.g., a photon detector with one or more optics). LiDAR system 100transmits light pulse 102 along path 104 as determined by the steeringsystem of LiDAR system 100. In the depicted example, light pulse 102,which is generated by the laser light source, is a short pulse of laserlight. Further, the signal steering system of the LiDAR system 100 is apulse signal steering system. However, it should be appreciated thatLiDAR systems can operate by generating, transmitting, and detectinglight signals that are not pulsed can be used to derive ranges to objectin the surrounding environment using techniques other thantime-of-flight. For example, some LiDAR systems use frequency modulatedcontinuous waves (i.e., “FMCW”). It should be further appreciated thatany of the techniques described herein with respect to time-of-flightbased systems that use pulses also may be applicable to LiDAR systemsthat do not use one or both of these techniques.

Referring back to FIG. 1 (a time-of-flight LiDAR system that uses lightpulses) when light pulse 102 reaches object 106, light pulse 102scatters and returned light pulse 108 will be reflected back to system100 along path 110. The time from when transmitted light pulse 102leaves LiDAR system 100 to when returned light pulse 108 arrives back atLiDAR system 100 can be measured (e.g., by a processor or otherelectronics within the LiDAR system). This time-of-flight combined withthe knowledge of the speed of light can be used to determine therange/distance from LiDAR system 100 to the point on object 106 wherelight pulse 102 scattered.

By directing many light pulses, as depicted in FIG. 2, LiDAR system 100scans the external environment (e.g., by directing light pulses 102,202, 206, 210 along paths 104, 204, 208, 212, respectively). As depictedin FIG. 3, LiDAR system 100 receives returned light pulses 108, 302, 306(which correspond to transmitted light pulses 102, 202, 210,respectively) back after objects 106 and 214 scatter the transmittedlight pulses and reflect pulses back along paths 110, 304, 308,respectively. Based on the direction of the transmitted light pulses (asdetermined by LiDAR system 100) as well as the calculated range fromLiDAR system 100 to the points on objects that scatter the light pulses(e.g., the points on objects 106 and 214), the surroundings within thedetection range (e.g., the field of view between path 104 and 212,inclusively) can be precisely plotted (e.g., a point cloud or image canbe created).

If a corresponding light pulse is not received for a particulartransmitted light pulse, then it can be determined that there are noobjects that can scatter sufficient amount of signal for the LiDAR lightpulse within a certain range of LiDAR system 100 (e.g., the max scanningdistance of LiDAR system 100). For example, in FIG. 2, light pulse 206will not have a corresponding returned light pulse (as depicted in FIG.3) because it did not produce a scattering event along its transmissionpath 208 within the predetermined detection range. LiDAR system 100 (oran external system communication with LiDAR system 100) can interpretthis as no object being along path 208 within the detection range ofLiDAR system 100.

In FIG. 2, transmitted light pulses 102, 202, 206, 210 can betransmitted in any order, serially, in parallel, or based on othertimings with respect to each other. Additionally, while FIG. 2 depicts a1-dimensional array of transmitted light pulses, LiDAR system 100optionally also directs similar arrays of transmitted light pulses alongother planes so that a 2-dimensional array of light pulses istransmitted. This 2-dimensional array can be transmitted point-by-point,line-by-line, all at once, or in some other manner. The point cloud orimage from a 1-dimensional array (e.g., a single horizontal line) willproduce 2-dimensional information (e.g., (1) the horizontal transmissiondirection and (2) the range to objects). The point cloud or image from a2-dimensional array will have 3-dimensional information (e.g., (1) thehorizontal transmission direction, (2) the vertical transmissiondirection, and (3) the range to objects).

The density of points in point cloud or image from a LiDAR system 100 isequal to the number of pulses divided by the field of view. Given thatthe field of view is fixed, to increase the density of points generatedby one set of transmission-receiving optics, the LiDAR system shouldfire a pulse more frequently, in other words, a light source with ahigher repetition rate is needed. However, by sending pulses morefrequently the farthest distance that the LiDAR system can detect may bemore limited. For example, if a returned signal from a far object isreceived after the system transmits the next pulse, the return signalsmay be detected in a different order than the order in which thecorresponding signals are transmitted and get mixed up if the systemcannot correctly correlate the returned signals with the transmittedsignals. To illustrate, consider an exemplary LiDAR system that cantransmit laser pulses with a repetition rate between 500 kHz and 1 MHz.Based on the time it takes for a pulse to return to the LiDAR system andto avoid mix-up of returned pulses from consecutive pulses inconventional LiDAR design, the farthest distance the LiDAR system candetect may be 300 meters and 150 meters for 500 kHz and 1 Mhz,respectively. The density of points of a LiDAR system with 500 kHzrepetition rate is half of that with 1 MHz. Thus, this exampledemonstrates that, if the system cannot correctly correlate returnedsignals that arrive out of order, increasing the repetition rate from500 kHz to 1 Mhz (and thus improving the density of points of thesystem) would significantly reduce the detection range of the system.

FIG. 4 depicts a logical block diagram of LiDAR system 100, whichincludes light source 402, signal steering system 404, pulse detector406, and controller 408. These components are coupled together usingcommunications paths 410, 412, 414, 416, and 418. These communicationspaths represent communication (bidirectional or unidirectional) amongthe various LiDAR system components but need not be physical componentsthemselves. While the communications paths can be implemented by one ormore electrical wires, busses, or optical fibers, the communicationpaths can also be wireless channels or open-air optical paths so that nophysical communication medium is present. For example, in one exemplaryLiDAR system, communication path 410 is one or more optical fibers,communication path 412 represents an optical path, and communicationpaths 414, 416, 418, and 420 are all one or more electrical wires thatcarry electrical signals. The communications paths can also include morethan one of the above types of communication mediums (e.g., they caninclude an optical fiber and an optical path or one or more opticalfibers and one or more electrical wires).

LiDAR system 100 can also include other components not depicted in FIG.4, such as power buses, power supplies, LED indicators, switches, etc.Additionally, other connections among components may be present, such asa direct connection between light source 402 and light detector 406 sothat light detector 406 can accurately measure the time from when lightsource 402 transmits a light pulse until light detector 406 detects areturned light pulse.

FIG. 5 depicts a logical block diagram of one example of light source402 that is based on a fiber laser, although any number of light sourceswith varying architecture could be used as part of the LiDAR system.Light source 402 uses seed 502 to generate initial light pulses of oneor more wavelengths (e.g., 1550 nm), which are provided towavelength-division multiplexor (WDM) 504 via fiber 503. Pump 506 alsoprovides laser power (of a different wavelength, such as 980 nm) to WDM504 via fiber 505. The output of WDM 504 is provided to pre-amplifiers508 (which includes one or more amplifiers) which provides its output tocombiner 510 via fiber 509. Combiner 510 also takes laser power frompump 512 via fiber 511 and provides pulses via fiber 513 to boosteramplifier 514, which produces output light pulses on fiber 410. Theoutputted light pulses are then fed to steering system 404. In somevariations, light source 402 can produce pulses of different amplitudesbased on the fiber gain profile of the fiber used in the source.Communication path 416 couples light source 402 to controller 408 (FIG.4) so that components of light source 402 can be controlled by orotherwise communicate with controller 408. Alternatively, light source402 may include its own controller. Instead of controller 408communicating directly with components of light source 402, a dedicatedlight source controller communicates with controller 408 and controlsand/or communicates with the components of light source 402. Lightsource 402 also includes other components not shown, such as one or morepower connectors, power supplies, and/or power lines.

Some other light sources include one or more laser diodes, short-cavityfiber lasers, solid-state lasers, and/or tunable external cavity diodelasers, configured to generate one or more light signals at variouswavelengths. In some examples, light sources use amplifiers (e.g.,pre-amps or booster amps) include a doped optical fiber amplifier, asolid-state bulk amplifier, and/or a semiconductor optical amplifier,configured to receive and amplify light signals.

Returning to FIG. 4, signal steering system 404 includes any number ofcomponents for steering light signals generated by light source 402. Insome examples, signal steering system 404 may include one or moreoptical redirection elements (e.g., mirrors or lens) that steer lightpulses (e.g., by rotating, vibrating, or directing) along a transmitpath to scan the external environment. For example, these opticalredirection elements may include MEMS mirrors, rotating polyhedronmirrors, or stationary mirrors to steer the transmitted pulse signals todifferent directions. Signal steering system 404 optionally alsoincludes other optical components, such as dispersion optics (e.g.,diffuser lenses, prisms, or gratings) to further expand the coverage ofthe transmitted signal in order to increase the LiDAR system 100'stransmission area (i.e., field of view). An example signal steeringsystem is described in U.S. Patent Application Publication No.2018/0188355, entitled “2D Scanning High Precision LiDAR UsingCombination of Rotating Concave Mirror and Beam Steering Devices,” thecontent of which is incorporated by reference in its entirety herein forall purposes. In some examples, signal steering system 404 does notcontain any active optical components (e.g., it does not contain anyamplifiers). In some other examples, one or more of the components fromlight source 402, such as a booster amplifier, may be included in signalsteering system 404. In some instances, signal steering system 404 canbe considered a LiDAR head or LiDAR scanner.

Some implementations of signal steering systems include one or moreoptical redirection elements (e.g., mirrors or lens) that steersreturned light signals (e.g., by rotating, vibrating, or directing)along a receive path to direct the returned light signals to the lightdetector. The optical redirection elements that direct light signalsalong the transmit and receive paths may be the same components (e.g.,shared), separate components (e.g., dedicated), and/or a combination ofshared and separate components. This means that in some cases thetransmit and receive paths are different although they may partiallyoverlap (or in some cases, substantially overlap).

FIG. 6 depicts a logical block diagram of one possible arrangement ofcomponents in light detector 404 of LiDAR system 100 (FIG. 4). Lightdetector 404 includes optics 604 (e.g., a system of one or more opticallenses) and detector 602 (e.g., a charge coupled device (CCD), aphotodiode, an avalanche photodiode, a photomultiplier vacuum tube, animage sensor, etc.) that is connected to controller 408 (FIG. 4) viacommunication path 418. The optics 604 may include one or more photolenses to receive, focus, and direct the returned signals. Lightdetector 404 can include filters to selectively pass light of certainwavelengths. Light detector 404 can also include a timing circuit thatmeasures the time from when a pulse is transmitted to when acorresponding returned pulse is detected. This data can then betransmitted to controller 408 (FIG. 4) or to other devices viacommunication line 418. Light detector 404 can also receive informationabout when light source 402 transmitted a light pulse via communicationline 418 or other communications lines that are not shown (e.g., anoptical fiber from light source 402 that samples transmitted lightpulses). Alternatively, light detector 404 can provide signals viacommunication line 418 that indicate when returned light pulses aredetected. Other pulse data, such as power, pulse shape, and/orwavelength, can also be communicated.

Returning to FIG. 4, controller 408 contains components for the controlof LiDAR system 100 and communication with external devices that use thesystem. For example, controller 408 optionally includes one or moreprocessors, memories, communication interfaces, sensors, storagedevices, clocks, ASICs, FPGAs, and/or other devices that control lightsource 402, signal steering system 404, and/or light detector 406. Insome examples, controller 408 controls the power, rate, timing, and/orother properties of light signals generated by light source 402;controls the speed, transmit direction, and/or other parameters of lightsteering system 404; and/or controls the sensitivity and/or otherparameters of light detector 406.

Controller 408 optionally is also configured to process data receivedfrom these components. In some examples, controller determines the timeit takes from transmitting a light pulse until a corresponding returnedlight pulse is received; determines when a returned light pulse is notreceived for a transmitted light pulse; determines the transmitteddirection (e.g., horizontal and/or vertical information) for atransmitted/returned light pulse; determines the estimated range in aparticular direction; and/or determines any other type of data relevantto LiDAR system 100.

FIG. 7 depicts an embodiment of a signal steering system (e.g., signalsteering system 404 of FIG. 4) according to some embodiments of thepresent technology. Polygon 702 has ten reflective sides (sides702A-702E are visible in FIG. 7) but can have any number of reflectivesides. For example, other examples of polygon 702 has 6, 8, or 20sides). Polygon 702 rotates about axis 703 based on a drive motor (notshown) to scan signals delivered from a light source (e.g., via output706, which is connected to a light source such as light source 402described above) along a direction perpendicular or at a non-zero angleto axis of rotation 703.

Mirror galvanometer 704 is positioned next to polygon 702 so that one ormore signals emitted from light source output 706 (e.g., a fiber tip)reflect off of mirror galvanometer 704 and onto rotating polygon 702.Mirror galvanometer 704 tilts so as to scan one or more signals fromoutput 706 to a direction different than the direction that polygon 702scans signals (e.g., edges 704A and 704B tilt towards and away frompolygon 702 about axis so as to scan pulses along a path that isparallel or at an angle to the axis of rotation of polygon 702). In someexamples, polygon 702 is responsible for scanning one or more signals inthe horizontal direction of the LiDAR system and mirror galvanometer 704is responsible for scanning one or more signals in the verticaldirection. In some other examples, polygon 702 and mirror galvanometer704 are configured in the reverse manner. While the example in FIG. 7uses a mirror galvanometer, other components can be used in its place.For example, one or more rotating mirrors or a grating (with differentwavelength pulses) may be used. The solid black line represents oneexample signal path through the signal steering system.

Light returned from signal scattering (e.g., when a light hits anobject) within region 708 (indicated by dashed lines) is returned torotating polygon 702, reflected back to mirror galvanometer 704, andfocused by lens 710 onto detector 712. While lens 710 is depicted as asingle lens, in some variations it is a system of one or more optics.

FIG. 8 depicts a similar system as depicted in FIG. 7 except a secondlight source is added that provides one or more signals from output 714.The light source for output 714 may be the same or different than thelight source for output 706, and the light transmitted by output 714 mayhave the same or a different wavelength as the light transmitted byoutput 706. Using multiple light outputs can increase the points densityof a points map without sacrificing the maximum unambiguous detectionrange of the system. For example, light output 714 can be positioned totransmit light at a different angle from output 706. Because of thedifferent angles, light transmitted from light source 706 is directed toan area different from light transmitted from output 714. The dottedline shows one example pulse path for pulses emitted from output 714.Consequently, one or more objects located at two different areas withina region can scatter and return light to the LiDAR system. For example,the region 716 (the dashed/double-dotted line) indicates the region fromwhich return signals from scattered signals returns to the LiDAR system.The returned light is reflected off polygon 702 and mirror galvanometer704 and focused on detectors 712 and 718 by lens 710. Detectors 712 and718 can each be configured to receive returned light from one of theoutputs 706 and 714, and such configuration can be achieved by preciselycontrolling the position of the detectors 712 and 718 as well as thewavelength(s) of the transmitted light. Note that the same lens (oroptic system) can be used for both detector 712 and 718. The offsetbetween outputs 706 and 714 means that the light returned to the LiDARsystem will have a similar offset. By properly positioning detectors 712and 718 based on the relative positioning of their respective lightsource outputs (e.g., respective positions of outputs 706 and 714) and,optionally, by properly controlling the wavelength(s) of the transmittedlight, the returned light will be properly focused on to the correctdetectors, and each received light can be a point in the points map.Therefore, compare to the system with only one output 706, the systemwith two outputs can maintain the same pulse repetition rate and producetwice the number of points or reduce the pulse repetition rate by halfand still produce the same number of points. As a non-limiting example,a system with two light outputs can reduce the pulse repetition ratefrom 1 MHz to 500 KHz, thereby increasing its maximum unambiguousdetection range from 150 meters to 300 meters, without sacrificingpoints density of the resulting points map. A pulse repetition rate ofbetween 200 and 2 MHz is contemplated and disclosed.

FIG. 9 depicts a point map from a first design. This design has twochannels (e.g., two light source outputs and two light detectors) placedin a way that the exiting beams have an angle of 8 degrees vertically.The scanned pattern has vertical overlap. The scanned range is +−56degrees horizontally and +12˜−20 degrees vertically.

FIG. 10 depicts a point map from a second design. This design has twochannels (e.g., two light source outputs and two light detectors) placedin a way that the exiting beams have an angle of 6 degrees. The scannedpattern has horizontal overlap (+−45 degrees). The scanned range is +−67degrees horizontally and +12˜−20 degrees vertically.

Exiting beams of two channels are not necessary to separate with acertain angle (e.g. 6 degree in FIG. 10) to obtain a larger horizontalrange. Horizontal displacement of existing beams can be used to expandthe horizontal range. For example, two exit beams may be pointed thatsame angle, but are offset with respect to each other in the same plane.Due to these different positions, each channel is reflected by differentpart of polygon and therefore covers a different horizontal range. Bycombining the two channels, the total horizontal range is increased.

FIG. 11 depicts a point map from a third design. This design has threechannels (e.g., three light source outputs and three light detectors) toincrease point density. About 2.88 million points per second can beobtained by using 3 fiber tips and 3 detectors. The resolution can befurther reduced to 0.07 degrees for both directions. The speed of thepolygon can be reduced to 6000 rpm.

FIG. 12 shows illustrative field of view (FOV) 1200 of a LiDAR systemaccording to an embodiment. As shown, FOV 1200 is a two-dimensionalspace bounded by X and Y dimensions. Although the LiDAR system cancollect data points from the entirety of FOV 1200, certain regions ofinterest (ROI) may have higher precedence over other regions within FOV1200 (e.g., such as undesired regions that occupy all space within FOV1200 that is not a ROI).

FIG. 12 shows five different illustrative ROIs 1210-1214 to illustratedifferent regions within FOV 1200 that require additional data pointsthan other regions within FOV 1200. For example, ROI 1210 occupies anentire band of a fixed y-axis height across the x-axis of FOV 1200. ROIs1211 and 1212 show localized ROIs below ROI 1210, and ROIs 1213 and 1214show localized ROIs above ROI 1210. It should be understood that anynumber of ROIs may exist and that the ROIs can occupy any portion of FOV1200. Embodiments discussed herein enable additional data points to becollected in the ROIs in a manner that does not disrupt the operation ofthe LiDAR system. That is, a LiDAR scanning system may scan the entiretyof FOV 1200 each scan cycle, while controlling one or more parameters toobtain additional data points from (or increase resolution) of the ROIs1211-1214.

FIG. 13 shows an illustrative block diagram of LiDAR system 1300according to an embodiment. LiDAR system 1300 can include lasersubsystem 1310, receiver system 1320, laser controller 1330, region ofinterest controller 1340, polygon structure 1350, polygon controller1355, mirror 1360, and mirror controller 1365. LiDAR system 1300 may becontained within one or more housings. In multiple housing embodiments,at least one of the housings may be a temperature controlled environmentin which selection portions of LiDAR system 1300 (e.g., laser controller1330, laser source 1312, controller 1340) are contained therein.

Laser subsystem 1310 may be operative to direct light energy towardsmirror 1360, which redirects the light energy to polygon structure 1350.Mirror 1360 also operative to redirect light energy received frompolygon structure 1350 to receiver system 220. Mirror 1360 may be movedunder the control of mirror controller 1365, which can control the speedand direction of mirror movement. As mirror 1360 moves, it causes lightbeing transmitted by laser subsystem 1310 to interface with differentportions of polygon structure 1350. Polygon structure 1350 is movingunder the control of polygon controller 1355 and is operative to directthe light energy received from mirror 1360 in accordance with the fieldof view parameters of LiDAR system 1300. That is, if LiDAR system 1300has a field of view with range of z, a lateral angle of x, and verticalangle of y, the range z can be controlled by the power of laser source1312, the vertical angle y can be controlled by the movement of mirror1360, and the lateral angle x can be controlled by polygon structure1350. It should be appreciated that in the alternative, the verticalangle can controlled by the polygon structure 1350 and that the lateralangle can be controlled by mirror 1360. Light energy that is reflectedback from objects in the field of view and returns to polygon structure1350 where it is directed back to mirror 1360, which redirects it backto receiver system 1320.

As defined herein, a frame rate may refer to the time it takes forscanning system 1302 to complete one full scan of the FOV. For eachframe, scanning system 1302 can obtain data points from each row (orcolumn) of a plurality of rows (or columns) that are defined by the FOV.Each row may correspond to a vertical angle within the vertical range ofthe FOV. The vertical angle can be controlled by mirror 1360. As mirror1360 moves, the vertical angle changes, thereby enabling scanning system1302 to obtain data points from multiple rows within the FOV. Verticalangle resolution refers spacing between adjacent rows of data points. Anincrease in vertical angular resolution corresponds to denser spacingbetween adjacent rows, and such an increase can be achieved bydecreasing the delta of the vertical angles between adjacent verticalangles. The delta between adjacent vertical angels can be decreased byslowing down the movement of mirror 1360. That is, as mirror movementspeed slows down, the change in the vertical angle delta decreases. Adecrease in vertical angular resolution corresponds to sparser spacingbetween adjacent rows, and such a decrease can be achieved by increasingthe vertical angle delta. The delta between adjacent vertical angels canbe increased by speeding up the movement of mirror 1360. That is, asmirror movement speeds up, the change in the vertical angle deltaincreases.

The plurality of data points obtained within any row may depend on ahorizontal angle within the horizontal range of the FOV. The horizontalrange may be controlled by polygon 1350, and the horizontal angleresolution may be controlled by a time interval of successive laserpulses. The time interval is sometimes related to the repetition rate. Asmaller time interval can result in increased horizontal angularresolution, and a larger time interval can result in decreasedhorizontal angular resolution.

The above reference to vertical and horizontal angles and vertical andhorizontal angular resolution was made in reference to a system in whichmirror 1360 controls the vertical angle. It should be understood thatmirror 1360 can be repurposed to control the horizontal angle and usedin a system different than that shown in FIG. 13.

Laser subsystem 1310 can include laser source 1312 and fiber tips1314-1316. Any number of fiber tips may be used as indicated the “n”designation of fiber tip 1316. As shown, each of fiber tips 1314-1316may be associated with laser source 1312. Laser source 1312 may be afiber laser or diode laser. Fiber tips 1314-1316 may be aligned in afixed orientation so that the light exiting each tip strikes mirror 1360at a particular location. The actual orientation may depend on severalfactors, including, for example, frame rate, mirror movement and speed,polygon speed, ROIs, repetition rate, etc. Additional discussion offiber tips and their characteristics in obtaining additional data pointswithin ROIs is discussed in more detail below.

Receiver system 1320 can include various components such as optics,detectors, control circuitry, and other circuitry. The optics maycontain light-transmitting optics that gather laser light returned frommirror 1360. Detectors may generate current or voltage signals whenexposed to light energy through the optics. The detectors may be, forexample, avalanche photo diodes. The outputs of the detectors can beprocessed by the control circuitry and delivered to a control system(not shown) to enable processing of return pulses.

Laser controller 1330 may be operative to control laser source 1312. Inparticular, laser controller 1330 can control power of laser source1312, can control a repetition rate or time interval of light pulsesemitted by laser source 1312 (via time interval adjustment module 1332),and can control pulse duration of laser source 1312. Time intervaladjustment module 1332 may be operative to control and/or adjust therepetition rate/time interval of the transmitter pulse of laser 1310.Time interval adjustment circuitry 1332 can vary the repetitionrate/time interval for different regions within the FOV. For example,the repetition rate may be increased for ROIs but may be decreased forareas of FOV that are not of interest. As another example, the timeinterval can be decreased for ROIs and increased for areas of FOV thatare not of interest.

Region of Interest controller 1340 may be operative to control LiDARsystem 1300 to obtain additional data points for the ROIs. That is, whenLiDAR system 1300 is scanning a ROI, ROI controller 1340 may causesystem 1300 to operate differently than when system 1300 is not scanninga ROI. ROI controller 1340 may control operation of laser controller1330, polygon controller 1355, and mirror controller 1365 to alter thequantity of data being obtained by system 1300. ROI controller 1340 mayreceive several inputs that dictate how it should control the scanningsubsystem 1302. The inputs can include, for example, frame rate 1342,sparse regions 1343, dense regions 1344, distance range, or any othersuitable input. Frame rate 1342 may specify the frequency at whichscanning subsystem 1302 completes a FOV scan. Sparse and dense regions1343 and 1344 may provide specific locations of ROIs. For example, denseregions 1344 may correspond to ROIs and sparse regions 1343 maycorrespond to regions within the FOV that are not ROIs. Fiber tip angles1345 may be used as a design constraint within which scanning sub-system1302 operates in order to optimally perform scanning.

Polygon structure 1350 may be constructed from a metal such as aluminum,plastic, or other material that can have a polished or mirrored surface.Polygon structure 1350 may be selectively masked to control the lateraldispersion of light energy being projected in accordance with the fieldof view of scanning subsystem 1302. Polygon structure 1350 can include anumber of facets to accommodate a desired horizontal field of view(FOV). The facets can be parallel or non-parallel to its symmetric axis.Polygon structure 1350 is operative to spin about an axis in a firstdirection at a substantially constant speed. The shape of polygonstructure 1350 can be trimmed (e.g., chop off the sharp corner or tip toreduce overall weight or required geometry envelope, chamfer the sharpedge to reduce air resistance) for better operational performance. SeeFIG.

Mirror 1360 may be a single plane or multi-plane mirror that oscillatesback and forth to redirect light energy emitted by laser source 1312 topolygon 1350. The single plane mirror may provide higher resolutions atthe top and bottom portions of the vertical field of view than themiddle portion, whereas the multi-plane mirror may provide higherresolution at a middle portion of the vertical field of view than thetop and bottom portions. Mirror 1360 may be a galvanometer. Varying theoscillation speed within an oscillation cycle can enable scanningsubsystem 1302 to acquire sparse or dense data points within the FOV.For example, if dense data points are required (for a particular ROI),the movement speed may be reduced, and if sparse data points arerequired (for non-ROIs), the movement speed may be increased.

FIG. 14 shows illustrative fiber tip arrangement according to anembodiment. Four fiber tips 1401-1404 are shown to be oriented withrespect to each other such that the same angle α exist between adjacentfiber tips. Multiple fiber tips (as opposed to just one fiber tip) maybe used so that high data collection is achieved. When an ROI is beingscanned, the mirror movement speed is adjusted to a ROI speed (e.g., aspeed that is slower than a sparse or non-ROI speed), the combination ofadditional fiber tips and reduced relative mirror movement speed yieldsdenser data capture. Moreover, when a non-ROI is being scanned, themirror movement speed operates at a non-ROI speed (e.g., a speed that isfaster than the ROI speed), the presence of multiple fiber tips ensuresthat sufficient data collection is achieved. The angle α may be selectedbased on properties of the light energy being emitted by each fiber tip(e.g., size), speed and movement characteristics of a mirror (e.g.,mirror 1360) for both ROIs and non-ROIs, and speed of the polygon (e.g.,polygon structure 1350). The angles between each of tips may be the sameor they can be different.

In some embodiments, all four fiber tips may be associated with the samelaser source. Thus, if the laser source is turned OFF, none of the fibertips will emit light energy. In another embodiment, each fiber tip maybe associated with its own respective laser source. This embodimentprovides a high degree of ON/OFF control of each fiber tip. In yetanother embodiment, a subset of the fiber tips may be associated withthe same laser source. For example, fiber tips FT1 and FT3 may share afirst common laser source, and fiber tips FT2 and FT4 may share a secondcommon laser source. This embodiment provides a balance between all ornone and individual ON/OFF control.

FIG. 15A shows a multiple mirror alignment arrangement (MMAA) 1500 thatmay be used for ROI and non-ROI embodiments. MMAA 1500 is an alternativeto using multiple fiber tips such as that shown in FIG. 14. As shown,MMAA 1500 shows collimator 1510, partial reflective mirrors 1521-1523,and reflective mirror 1524. Light energy originating from a laser source(not shown) is routed to collimator 1510, which directs light energy topartial reflective mirror 1521. Partial reflective mirror 1521 permits aportion of the light energy to pass through (shown as exit path 1531)and the remaining light energy is redirected to partial reflectivemirror 1522. Partial reflective mirror 1522 allows a portion of thelight energy to pass through to partial reflective mirror 1523. Partialreflective mirror 1522 redirects light energy along exit path 1532.Partial reflective mirror allows a portion of the light energy to passthrough to partial reflective mirror 1524. Partial reflective mirror1523 redirects light energy along exit path 1533. Reflective mirror 1524may redirect all or at least a portion of all the remaining light energyalong exit path 1534.

The angles between adjacent exit paths may be selected to achieve thedesired resolution for ROIs and non-ROIs. For example, angles betweenadjacent exit paths may be similar to the a angles shown in FIG. 14. Insome embodiments, the angle between adjacent exit paths may be fixed. Inother embodiments, the angle between adjacent exit paths may bevariable. Variable angle adjustment may be used to provide differentresolutions on demand. For example, if the LiDAR system is being used ina vehicle, the angles may be set to a first configuration when thevehicle operating in a first mode (e.g., driving at highway speeds orvehicle is driven by a first driver) and may be set to a secondconfiguration when the vehicle is operating in a second mode (e.g.,driving at city speeds or vehicle is driven by a second driver).

FIG. 15B shows another multiple mirror alignment arrangement (MMAA) 1501that may be used for ROI and non-ROI embodiments. MMAA 1501 is analternative to MMAA 1500. As shown, MMAA 1501 shows collimator 1512,partial reflective mirrors 1525-1527, reflective mirror 1528, and exitpaths 1535-1538. MMAA 1501 is similar to MMAA 1500 with exception of thepositioning of collimator 1512. As shown, collimator 1512 is positionedabove mirror 1525. If desired, collimator 1512 can be positioned belowmirror 1528. As a further alternative, collimator 1512 can be aimed at adifferent mirror such as mirror 1526 or mirror 1527, and such mirrorscan redirect the light energy as necessary to achieve the desiredresults.

FIG. 15C shows an illustrative multiple collimator arrangement 1550 thatmay be used for ROI and non-ROI embodiments. Arrangement 1550 caninclude collimators 1561-1563. Each of collimators 1561-1563 may beassociated with its own laser source. Associating each collimator withits own laser source enables selective turning ON and OFF of lightenergy emanating from each collimator. For sparse regions, one or moreof the laser sources may be turned OFF (to save power) and for denseregions, all laser sources may be turned ON to maximize resolution. Eachof collimators 1561-1563 may be fixed in a particular orientation toachieve the desired a angle between each collimator. If desired, each ofcollimators 1561-1563 may be movable to dynamically adjust the a anglebetween each collimator.

FIG. 15D shows an illustrative collimator and lens arrangement 1570 thatmay be used to control divergence of the light beam existing collimator1571 according to an embodiment. Lens 1572 may be moved towards and awayfrom collimator 1571 to adjust divergence of the light beam. Arrangement1570 may be used to adjust the size of the light beam as it is projectedby the scanning system. For ROI regions, it may be desirable to have arelatively narrow beam. To produce a relatively narrow beam, lens 1572may positioned at a narrow beam distance away from the collimator 1571.For non-ROI regions, it may be desirable to have a relatively wide beam.To produce a relatively wide beam, lens 1572 may positioned at a widebeam distance away from the collimator 1571.

FIG. 16 shows illustrative scanning resolution using multiple fibertips, a multiple mirror alignment arrangement, or multiple collimatorarrangement according to an embodiment. The illustrative verticalresolution lines from fiber tips (FT1-FT4) are shown. The resolutionlines are grouped according to sparse resolution and dense resolution asshown. In sparse regions, the scanning system is moving the mirror at arelatively faster speed than when in the dense region, and in denseregions, the scanning system is moving the mirror at a relatively slowerspeed than when in the sparse region. The spacing between the adjacentscanning lines (as shown by the repeated pattern of FT₁-FT₄) issubstantially equidistant. This equidistant spacing may be made possibleby coordinating the alignment of the fiber tips with the frame rate,mirror speed, polygon speed, and any other suitable factors. Incontrast, if alignment of fiber tips is not properly coordinated, theequidistant spacing may not be possible, thereby yielding an undesirablescanning pattern. In the dense region, each fiber tip may providemultiple lines of resolution. For example, as shown, FT₁ provides fourlines of resolution before FT₂ provides its four lines of resolution.Thus, each fiber tip provides four lines of resolution beforetransitioning to the next fiber tip. It should be understood that thenumber of lines of resolution provided by each fiber tip depends on anumber of factors, including, for example, mirror speed, polygon speed,and angle between fiber tips. The lines of resolution among fiber tipsmay interlace at the transition between the sparse and dense regions.For example, at least one line of resolution from one or more of fibertips FT₂-FT₄ may be interlaced among the four lines of resolutionpertaining to FT₁ (as shown in FIG. 17A).

The angle between the fiber tips (e.g., the a) may be selected based onthe mirror speeds, polygon speed, desired angular resolution of the ROI,and a requirement for the spacing between the resolution lines in thesparse region(s) to be substantially equidistant to each other. At leasttwo different mirror speeds are used to provide the dense and sparseresolutions, and it is the variance in mirror speeds that can cause theresolution lines to be non-equidistant if the angles between fiber tipsare not properly aligned. For example, assume that the angle of thedense region is θ. θ can represent the total degrees within the FOV thatare part of the ROI and require dense resolution. If the mirror speed isconstant throughout the entire frame, the angle between fiber tips, α,can be approximately θ/n, where n is the number of fiber tips. This acs,referred to as angle with constant speed may represent a target anglefor the fiber tips, but additional calculations are required to takeinto account that the mirror operates at different speeds, and as aresult α, cannot be set to exactly θ/n. The sparse regions must be takeninto account. In the sparse region, assume that the desired anglebetween adjacent lines of resolution is ϕ. For the example, ϕ may existbetween FT₁ and FT₂, between FT₂ and FT₃, between FT₃ and FT₄, betweenFT₄ and FT₁ in the sparse region. In order to achieve ϕ betweendifferent fiber tips, the angle between fiber tips can be calculated bythe following equation:

α=α_(vs) =ϕ*n*2−ϕ

where α_(vs) is the angle with a variable speed mirror, ϕ is the anglebetween adjacent lines of resolution within the sparse region, n is thenumber of fiber tips, and the number 2 is a scaling factor to take intoaccount overlapping lines of resolution. The variables of ϕ, n, mirrorspeed, and polygon speed are selected such that α_(vs) is the same as orapproximately the same as α_(cs). Selecting the variables such thatα_(vs) is the same as or approximately the same as α_(cs), enables thescanning system to achieve the desired scanning densities for both ROIand non-ROI regions within the FOV each frame.

FIG. 17A shows another illustrative diagram of vertical resolution usingmultiple fiber tips or a multiple mirror alignment arrangement,according to an embodiment. Sparse regions and a dense region are shown.Four fiber tips FT₁-4 are used. In the sparse region, the resolutionlines for each fiber tip are evenly spaced. In the dense region, thevertical lines of resolution are substantially more dense than thevertical lines of resolution in the sparse regions. Within the denseretention, the vertical lines of resolution are grouped predominantlyfor each fiber tip, however, interlacing resolution lines from otherfiber tips may exist within a particular group.

FIG. 17B shows an illustrative close-up view of a sparse region withinFIG. 17A and FIG. 17C shows an illustrative close-up view of the denseregion within FIG. 17A, according to various embodiments. Note that thescaling factor in FIG. 17B is less zoomed in than it is in FIG. 17C. Asa result, FIG. 17B shows lines of resolution for multiple fiber tips,and where FIG. 17C shows multiple lines of resolution for only one fibertip.

The dynamic resolution discussed above has been in the context ofdynamic vertical resolution. If desired, the laser subsystem (e.g., thefiber tips, multiple mirror alignment arrangement, or multiplecollimator arrangement) can be oriented in a horizontal direction (asopposed to the above-described vertical direction) to provide dynamichorizontal resolution.

Assuming speed changes to mirror movement are used to control thevertical resolution, the repetition rate or time interval can be changedto dynamically control the horizontal resolution. This provides dualaxis dynamic resolution control that can be synchronized by a controller(e.g., ROI controller 1340) to provide increased resolution for ROIs anddecreased resolution for non-ROIs for both vertical and horizontalorientations. For example, when the scan cycle comes across an ROI, themirror movement speed is decreased and the time interval betweensuccessive light pulses is decreased (thereby increasing repetitionrate). When the scan cycle comes across a non-ROI, the mirror movementspeed is increased and the time interval between successive light pulsesis increased (thereby decreasing repetition rate).

In some embodiments, the laser source(s) can be selectively turned ONand OFF to provide vertical dynamic range (assuming the laser subsystemis oriented as such). This can eliminate the need to adjust the mirrorspeed to achieve dynamic vertical resolution. If desired, however, thelaser source(s) can be selectively turned ON and OFF in conjunction withvariations in mirror movement speed.

FIG. 18 shows illustrative FOV 1800 with variable sized laser pulsesaccording to an embodiment. FOV 1800 includes two sparse regions and onedense region as shown. Both the sparse and dense regions showillustrative light pulses that take the form of different sized circles.The sparse sized circles are larger than the dense sized circles. Whenthe scanning system is projecting light to sparse region, the mirrorspeed may be moving at a sparse speed and the repetition rate may be setto a sparse region repetition rate. Conversely, when the scanning systemis projecting light to the dense region, the mirror speed may be movingat the dense speed and the repetition rate may be set to a dense regionrepetition rate. The sparse speed is faster than the dense speed and thesparse region repetition rate is slower than the dense region repetitionrate. As a result, there are fewer light pulses being sent into thesparse region than in the dense region. If the circle size of the lightpulses projected into the sparse region were the same size as thecircles in the dense region, underfilling could exist. Underfill mayoccur when too much space exists between adjacent light pulse circles.Thus, in order to minimize underfill, it is desirable to project anappropriately sized light pulse for both the sparse and dense regions.

Control over light pulse divergence can be exercised using a curvedmirror with an integrated planar portion. Such a curved mirror may beused as mirror 1360. FIG. 19A shows an illustrative mirror mirror 1900arranged to include curved mirror portion 1902, planar portion 1904, andcurved mirror portion 1906. Planar portion 1904 is positioned betweencurved mirror portions 1902 and 1906. Curved mirror portions 1902 and1906 generate a convergence of light pulses to create a relativelylarger sized circle (for the sparse regions). Planar portion 1904 maynot alter the size of the light pulse interacting with it, and usedprojecting light into the dense region.

FIG. 19B shows another illustrative mirror 1950 according to anembodiment. Mirror 1950 may include a curved mirror portions 1952 and1956 and planar portion 1954. In some embodiments, planar portion 1954may be a prism (e.g., similar to that shown in the mirror of FIG. 21).

FIG. 19C shows another illustrative mirror 1960 that incorporates aconcave continuously curved portion 1961 between two planar portions1962 and 1963 according to an embodiment. The laser beam(s) is/aredirected to portion 1961 and any return pulses can be reflected byplanar portions 1962 and 1963. FIG. 19D shows yet another illustrativemirror 1970 that incorporates a concave step-wise curved portion 1971between two planar portions 1972 and 1973 according to an embodiment.The laser beam(s) is/are directed to portion 1971 and any return pulsescan be reflected by planar portions 1972 and 1973. FIG. 19E shows yetanother illustrative mirror 1980 that incorporates a convex continuouslycurved portion 1981 between two planar portions 1982 and 1983 accordingto an embodiment. The laser beam(s) is/are directed to portion 1981 andany return pulses can be reflected by planar portions 1982 and 1983.FIG. 19F shows another illustrative mirror 1990 that incorporates aconvex step-wise curved portion 1961 between two planar portions 1962and 1963 according to an embodiment. The laser beam(s) is/are directedto portion 1991 and any return pulses can be reflected by planarportions 1992 and 1993.

FIG. 19G shows another illustrative mirror 1965 that incorporates aconcave portion 1966 between two planar portions 1967 and 1968 accordingto an embodiment. Concave portion 1966 has a flat portion positionedbetween two curved portions. The curved portions are convex with respectto the incoming laser beam. The laser beam(s) is/are directed to portion1966 and any return pulses can be reflected by planar portions 1967 and1968. FIG. 19H shows yet another illustrative mirror 1975 thatincorporates a concave curved portion 1976 between two planar portions1977 and 1978 according to an embodiment. Concave portion 1976 has aflat portion positioned between two curved portions. The curved portionsare concave with respect to the incoming laser beam. The laser beam(s)is/are directed to portion 1976 and any return pulses can be reflectedby planar portions 1977 and 1978. FIG. 19I shows yet anotherillustrative mirror 1985 that incorporates a convex portion 1986 betweentwo planar portions 1987 and 1988 according to an embodiment. Convexportion 1986 has a flat portion positioned between two curved portions.The curved portions are convex with respect to the incoming laser beam.The laser beam(s) is/are directed to portion 1986 and any return pulsescan be reflected by planar portions 1987 and 1988. FIG. 19J showsanother illustrative mirror 1995 that incorporates a convex portion 1996between two planar portions 1997 and 1998 according to an embodiment.Convex portion 1996 has a flat portion positioned between two curvedportions. The curved portions are concave with respect to the incominglaser beam. The laser beam(s) is/are directed to portion 1996 and anyreturn pulses can be reflected by planar portions 1997 and 1998.

FIG. 20 depicts a similar system as depicted in FIG. 8 except mirror 704includes prism 2020 and light sources 706 and 708 are moved out of thescan areas for detectors 708 and 712. Placing light sources 706 and 708out of the return paths for detectors 708 and 712 reduces or eliminatesany interference that may occur. It should be understood that the sizeof prism 2020 is shown in an exaggerated size for illustrative purposes,and that the size of prism is preferably minimized to lessen its impacton the return paths.

FIG. 21 depicts a similar system as that shown in FIG. 20, except thatmirror 704 is replaced with a curved mirror 2104 (e.g., similar tocurved mirror 1950). Curved mirror 2104 can include planar portion 2105,which may be a prism, and curved mirror portions 2106 and 2107. Use ofcurved mirror 2104 can perform double duty of generating different sizedlaser pulses (as discussed above in connection with FIG. 18 and as afocusing lens 710. As such, lens 710 can be eliminated in the embodimentshown in FIG. 21.

FIGS. 9-11 discussed above each show a curve in the data points beingacquired in their respective fields of view. The curve can be flattenedby using a polygon that has a trapezoidal cross-section such as thatshown in FIG. 22. FIG. 22 shows an illustrative polygon 2200 thatrotates around rotation axis 2202. Note that the sequence of lighttravel is different for FIG. 22 than it is for FIG. 13, in that thesource light strikes polygon 2200 before interacting with mirror 2230.It should be appreciated that the light source can strike mirror 2230before interacting with polygon 2200. FIG. 22 also shows illustrativemirror 2230 and exemplary light path 2240. Polygon 2200 may have atrapezoidal cross-section in which facet 2210 is not parallel to facet2212, but top and bottom surfaces 2220 and 2222 can be parallel to eachother. Rotation axis 2202 is not in line with gravity (the gravity axisis shown pointing straight down). That is, if rotation axis 2202 were inline with gravity, it would be parallel with the gravity line. Rotationaxis 2202 can be line with gravity, if desired. Rotation axis 2202 maybe angled with respect to gravity so that light energy being reflectedoff of polygon 2200 is pointed in a useful direction (e.g., towards theroad as opposed to the sky).

FIG. 23 depicts a point map using polygon 2200 of FIG. 22. The point mapincludes two channels (e.g., two light source outputs and two lightdetectors). The scanned pattern has vertical overlap and no curve in thevertical direction.

FIG. 24 shows an illustrative block diagram of LiDAR system 2400according to an embodiment. LiDAR system 2400 is similar to system 1300of FIG. 24, but includes additional components to extend the field ofview. Whereas system 1300 may provide 120 degrees of horizontal view,system 2400 may provide 360 degrees of horizontal view. System 2400 caninclude first subsystem 2410, second subsystem 2420, third subsystem2430, polygon 2440, polygon control 2444, and ROI controller 2450. Eachof first, second, and third subsystems 2410, 2420, and 2430 may sharepolygon 2440 and be controlled by the same ROI controller 2450. Ifdesired, each of subsystems 2410, 2420, and 2430 may be independentlycontrolled by their own respective ROI controller. ROI controller may besimilar to ROI controller 1340 of FIG. 13. Each of systems 2410, 2420,and 2430 can include a laser controller (e.g., similar to lasercontroller 1330), a laser subsystem (e.g., similar to laser subsystem1310), a receiver system (not shown), a mirror (e.g., similar to mirror1360), and mirror controller (e.g., similar to mirror controller 1365).LiDAR system 2400 may be contained within one or more housings. Any ofthe embodiments (e.g., FIGS. 1-23) discussed herein may be used insystem 2400.

In the embodiments shown in FIG. 24, each of subsystems 2410, 2420, and2430 can be responsible for observing a different portion (e.g., aparticular 120 degree portion) of a 360 degree field of view. Theobserved portions for each subsystem may or may not overlap. Eachsubsystem can be independently controlled to focus on ROI(s) in theirrespective FOVs. In other embodiments, four subsystems may be used (asopposed to three subsystems), each of the four subsystem may beresponsible for observing a 90 degree portion of the 360 degree field ofview. The observed portions for all four subsystems may or may notoverlap. In yet other embodiments, five of more subsystems may be used.

As discussed above, the LiDAR system can control the vertical andhorizontal angular resolution of the light beams being projected by thescanning system. The angular resolution determines how many points canbe observed from an object at a certain distance. To reiterate, thevertical angular resolution is defined by the vertical angle betweenadjacent light beam projections. As the vertical angle decreases, theseparation between adjacent light beams is decreased, thereby resultingin more data points (or increased angular resolution). As the anglebetween adjacent light beams increases, the separation between adjacentlight beams is increased, thereby resulting in fewer data points (ordecreased angular resolution). It may be desirable to acquire more datapoints for objects that are relatively far away than for objects thatare relatively close. See, for example, FIG. 25A, which shows closeobject 2505 and far object 2510 and the illustrative data pointscaptured from both objects. The vertical angular resolution in FIG. 25Ais constant across the entire vertical FOV. Close object data points2507 correspond to data points obtained from close object 2505 and farobject data points 2512 correspond to data points obtained from farobject 2510. As shown, the data points collected for far object 2510 arerelatively sparse compared to data points collected for close object2505.

FIG. 25B shows an illustrative scenario where the angular resolution isvariable across the vertical FOV. In particular, for regions 2560 and2562, the vertical angle delta is α and for region 2570, the verticalangle delta is β, where β is less than α. Far object data points 2552correspond to far object 2550. As compared to FIG. 25, the number ofdata points collected from the far object is greater when the angularresolution is increased such that density of light beams, andcorresponding number of data points being collected, is increased. Itshould be understood that although FIGS. 25A and 25B show angularresolution in the vertical FOV, angular resolution may also occur in thehorizontal FOV. The total number of data points that can be obtained areconstrained by design constraints of the LiDAR system. Therefore, it isdesirable to optimize the angular resolution for a given LiDAR systemfor one or more ROI(s).

The LiDAR system generally does not have a priori knowledge of theobject(s) it is trying to detect, but certain assumptions can be made,and based on these assumptions, the angular resolution can be customizedfor different portions of the FOV. For example, the angular resolutionmay be customized for ROI(s) and/or assumption exceptions. In a vehiclecontext, the center FOV may have the highest probability of containing arelevant object at distance. For example, in the vertical context, belowthe center FOV focuses on the ground, and above the center FOV focuseson the sky. Thus, the center vertical FOV is more desirable for improvedangular resolution. In the horizontal FOV context, left and rightfocusing is generally irrelevant at large distances. There may beexceptions as to where improved angular resolution is primarily focusedon the center FOV. Such exceptions may occur when the vehicle isturning, driving on a curved road, driving up and down hills, or anyother suitable situation where the center FOV is not the ideal ROI.

FIG. 26A shows an illustrative optimized angular resolution in avertical FOV with respect to the ground according to an embodiment. FIG.26B shows an illustrative graph of angular vertical resolution as afunction of the vertical angle in the FOV according to an embodiment. Asshown in FIG. 26B, the angular vertical resolution is variable betweenvertical angels of −25 degrees and −5 degrees, constant between verticalangles of −5 and 3 degrees, and variable between vertical angles of 3and 19 degrees. The variation in the angular resolution between −25 and−5 degrees is such that the ground distance between each adjacent lightbeam is substantially constant, as shown in FIG. 26A. The constantdistance in between adjacent light pulses is possible by continuouslyvarying the angular resolution. As discussed above, the angularresolution can be controlled by varying the movement speed of the mirror(e.g., mirror 1360). As shown in FIGS. 26A and 26B, the delta anglebetween adjacent light pulses increases in proportion to its relativeangle away from the zero vertical angle. For example, at −25 degrees,The delta angle within the center region (e.g., shown as −5 to 3degrees) is constant and represents the smallest angle differencebetween adjacent light pulses throughout the entire vertical FOV. Theangular resolution of the vertical angles above 3 degrees may becontinuously variable in same manner as the angular resolution for thevertical angles below −5 degrees. It should be appreciated that thenumbers used in FIG. 26B are merely illustrative and that ranges for thevariable angular values and the constant angular values may be differentthan that shown and described.

FIG. 27 shows an illustrative graph of step changing angular verticalresolution as a function of the vertical angle in the FOV according toan embodiment. Both step change vertical resolution line 2710 andcontinuous vertical resolution line 2720 are shown for comparisonpurposes. Step change vertical resolution line 2710 shows that thevertical resolution remains fixed for a fixed range of vertical anglesin FOV before changing to a different vertical resolution. Step changevertical resolution line 2710 may be easier to implement than continuousvertical resolution line 2720.

Implementation of the variable and constant angular resolution may beperformed using the embodiments described above in connection with FIGS.1-24 or any other system capable of adjusting the angular resolution.For example, the mirror speed can be variably adjusted to yield angularresolution angles of FIGS. 26B and 27.

FIG. 28 shows illustrative process 2800 for handing ROIs according to anembodiment. Process 2800 may be implemented in a system such as system1300 as discussed above. Starting at step 2810, at least one range ofinterest (ROI) region can be received within the LiDAR scanning systemfield of view (FOV), wherein any portion within the FOV not within theat least one ROI region is a non-ROI region or a region of non-interest.For example, a controller such as ROI controller 1340 may receive anindication of the ROIs. As a specific example, dense regions and sparseregions within the FOV may be provided or programmed to the ROIcontroller to specify ROIs and non-ROIs. The LiDAR scanning systemdirects light pulses to the FOV in a controlled manner by scanningacross each horizontal row according the horizontal boundary of the FOVfor multiple rows that comprise the vertical boundary of the FOV.

When the LiDAR scanning system is aimed at a non-ROI region, the LiDARscanning system can be operated at a first vertical scanning rate and ata first laser pulse interval (as indicated by step 2820). When the LiDARscanning system is aimed at a ROI region, the scanning system canoperate at a second vertical scanning rate and at a second a secondlaser pulse interval (as indicated by step 2830). The second laser pulseinterval can be slower than the first laser pulse interval.

It should be understood that the steps shown in FIG. 28 are merelyillustrative and that additional steps may be added or existing stepsmay be omitted.

FIG. 29 shows illustrative process 2900 for handing ROIs according to anembodiment. Starting at step 2910, a plurality of light beams can beemitted towards a scanning system that controls where the plurality oflight beams are directed within a field of view (FOV). For example, twoor more light beams may be directed to the FOV. Each of the plurality oflight beams are aligned at a fixed angle with respect to each other. Atstep 2920, when the scanning system is aimed at a region of interest(ROI) within the FOV, the plurality of light beams can yield a denseresolution. For example, the dense region is shown in FIG. 16 and FIG.17A. At step 2930, when the scanning system is aimed at a region ofnon-interest (RONI) within the FOV, the plurality of light beams canyield a sparse resolution (as illustrated in FIGS. 16 and 17A).

It should be understood that the steps shown in FIG. 29 are merelyillustrative and that additional steps may be added or existing stepsmay be omitted.

FIG. 30 shows illustrative process 3000 for handing ROIs according to anembodiment. Starting at step 3010, the LiDAR system can be used to scana field of view (FOV). The LiDAR system controls aim of at least onelight beam as it scans the FOV, and the FOV can be bounded by a firstdirectional degree range (e.g., vertical angles) and a seconddirectional degree range (e.g., horizontal angles). At step 3020, arange of interest (ROI) is defined within the FOV that occupies a firstportion of the first directional degree range. At step 3030, an angularresolution of the at least one light beam can be adjusted while theLiDAR system scans the FOV, wherein when the at least one light beam isaimed at the ROI, the angular resolution is constant throughout thefirst portion of the first directional degree range, and wherein thewherein when the at least one light beam is aimed at a region ofnon-interest (RONI), the angular resolution is varied across the firstdirectional degree range encompassing the RONI.

It should be understood that the steps shown in FIG. 30 are merelyillustrative and that additional steps may be added or existing stepsmay be omitted.

It is believed that the disclosure set forth herein encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Eachexample defines an embodiment disclosed in the foregoing disclosure, butany one example does not necessarily encompass all features orcombinations that may be eventually claimed. Where the descriptionrecites “a” or “a first” element or the equivalent thereof, suchdescription includes one or more such elements, neither requiring norexcluding two or more such elements. Further, ordinal indicators, suchas first, second or third, for identified elements are used todistinguish between the elements, and do not indicate a required orlimited number of such elements, and do not indicate a particularposition or order of such elements unless otherwise specifically stated.

Moreover, any processes described with respect to FIGS. 1-30, as well asany other aspects of the invention, may each be implemented by software,but may also be implemented in hardware, firmware, or any combination ofsoftware, hardware, and firmware. They each may also be embodied asmachine- or computer-readable code recorded on a machine- orcomputer-readable medium. The computer-readable medium may be any datastorage device that can store data or instructions which can thereafterbe read by a computer system. Examples of the computer-readable mediummay include, but are not limited to, read-only memory, random-accessmemory, flash memory, CD-ROMs, DVDs, magnetic tape, and optical datastorage devices. The computer-readable medium can also be distributedover network-coupled computer systems so that the computer readable codeis stored and executed in a distributed fashion. For example, thecomputer-readable medium may be communicated from one electronicsubsystem or device to another electronic subsystem or device using anysuitable communications protocol. The computer-readable medium mayembody computer-readable code, instructions, data structures, programmodules, or other data in a modulated data signal, such as a carrierwave or other transport mechanism, and may include any informationdelivery media. A modulated data signal may be a signal that has one ormore of its characteristics set or changed in such a manner as to encodeinformation in the signal.

It is to be understood that any or each module or state machinediscussed herein may be provided as a software construct, firmwareconstruct, one or more hardware components, or a combination thereof.For example, any one or more of the state machines or modules may bedescribed in the general context of computer-executable instructions,such as program modules, that may be executed by one or more computersor other devices. Generally, a program module may include one or moreroutines, programs, objects, components, and/or data structures that mayperform one or more particular tasks or that may implement one or moreparticular abstract data types. It is also to be understood that thenumber, configuration, functionality, and interconnection of the modulesor state machines are merely illustrative, and that the number,configuration, functionality, and interconnection of existing modulesmay be modified or omitted, additional modules may be added, and theinterconnection of certain modules may be altered.

Whereas many alterations and modifications of the present invention willno doubt become apparent to a person of ordinary skill in the art afterhaving read the foregoing description, it is to be understood that theparticular embodiments shown and described by way of illustration are inno way intended to be considered limiting. Therefore, reference to thedetails of the preferred embodiments is not intended to limit theirscope.

What is claimed is:
 1. A light detection and ranging (LiDAR) system,comprising: a beam steering system comprising: a polygon structure; anda mirror coupled to a mirror controller that controls movement speed anddirection of the mirror; a laser system operative to emit light pulsesthat are steered by the beam steering system in accordance with a fieldof view (FOV); and a region of interest (ROI) controller coupled to thebeam steering system and the laser system, the ROI controller operativeto: coordinate the movement speed of the mirror and light pulseintervals when the light pulses emitted by the laser system are steeredto at least one ROI within the FOV.
 2. The LiDAR system of claim 1,wherein the ROI controller is operative to: for light pulses steeredtowards the at least one ROI, control the movement speed of the mirrorsuch that it is slower compared to the movement speed of the mirror whenthe light pulses are steered towards a non-ROI.
 3. The LiDAR system ofclaim 1, wherein the ROI controller is operative to: adjust the movementspeed of the mirror based on a beam steering angle within the FOV. 4.The LiDAR system of claim 1, wherein the ROI controller is operative to:adjust a repetition rate of the light pulses based on the beam steeringangle.
 5. The LiDAR system of claim 1, wherein the ROI controller isoperative to: when the beam steering system is directed to an ROI: setthe movement speed to a ROI movement speed; and set the repetition rateto a ROI repetition rate; and when the beam steering system is directedto a non-ROI: set the movement speed to a non-ROI movement speed; andset the repetition rate to a non-ROI repetition rate, wherein the ROImovement speed is slower than the non-ROI movement speed, and whereinthe ROI repetition rate is faster than the non-ROI repetition rate. 6.The LiDAR system of claim 5, wherein the beam steering angle is avertical beam steering angle.
 7. The LiDAR system of claim 5, whereinthe beam steering angle is a horizontal beam steering angle.
 8. TheLiDAR system of claim 1, wherein the laser system comprises a pluralityof light emission paths each directed towards the beam steering system,wherein the light emission paths are aligned such that a fixed angleexists between any two immediately adjacent light emission paths.
 9. TheLiDAR system of claim 8, wherein the ROI controller is operative tocontrol the mirror movement speed based on the fixed angle, a frame ratein which the beam steering system scans the FOV, and the at least oneROI.
 10. The LiDAR system of claim 9, wherein the ROI controller isoperative to control the mirror movement speed based on a desiredangular resolution.
 11. The LiDAR system of claim 8, wherein the lasersystem comprises a plurality of fiber tips that are associated with acommon laser source, wherein each fiber tip is associated with arespective one the of the plurality of light emission paths.
 12. TheLiDAR system of claim 8, wherein the laser system comprises: acollimator associated with a laser source; and a plurality of partiallyreflective mirrors that redirect light energy being emitted from thecollimator along respective ones of the plurality of light emissionpaths.
 13. The LiDAR system of claim 1, wherein the laser systemcomprises a plurality of light emission paths each directed towards thebeam steering system, wherein each light emission path is associatedwith a collimator coupled to its own laser source.
 14. The LiDAR systemof claim 13, wherein an orientation of each collimator is adjustable tocontrol an angle between adjacent collimators.
 15. The LiDAR system ofclaim 1, further comprising: a receiver system comprising a focusinglens and at least one detector, wherein a scan region exist between thefocusing lens and the mirror; wherein the mirror comprises a prism; andwherein the laser system comprises at least one light emission pathsource positioned outside of the scan region and is directed towards theprism.
 16. The LiDAR system of claim 15, a receiver system comprising aplurality of detectors, wherein a scan region exist between the at leastone detector and the mirror; wherein the mirror comprises a planarportion flanked by a first curved mirror portion and a second curvedmirror portion; and wherein the laser system comprises a plurality oflight emission path sources positioned outside of the scan region andare directed towards the mirror.
 17. The LiDAR system of claim 16,wherein the first and second curved mirror portions are used to non-ROIregions, and wherein the planar portion is used for the at least one ROIregion.
 18. The LiDAR system of claim 1, wherein the polygon comprises atrapezoidal cross-section in which a first facet is not parallel to asecond facet.
 19. The LiDAR system of claim 1, wherein the trapezoidalcross-section produces a scanned pattern having vertical overlap but nocurve in a vertical direction.
 20. A method for using a light detectionand ranging (LiDAR) scanning system, comprising: receiving at least onerange of interest (ROI) region within the LiDAR scanning system field ofview (FOV), wherein any portion within the FOV not within the at leastone ROI region is a non-ROI region; when the LiDAR scanning system isaimed at a non-ROI region, operating the LiDAR scanning system at afirst vertical scanning rate and at a first laser pulse interval; andwhen the LiDAR scanning system is aimed at a ROI region, operating thescanning system at a second vertical scanning rate and at a second laserpulse interval, wherein the second scanning rate is slower than thefirst scanning rate.
 21. The method of claim 20, wherein the first andsecond laser pulse intervals are the same.
 22. The method of claim 20,wherein the first laser pulse interval is longer than the second laserpulse interval.
 23. A method for using a light detection and ranging(LiDAR) system, comprising: emitting a plurality of light beams towardsa scanning system that controls where the plurality of light beams aredirected within a field of view (FOV), wherein each of the plurality oflight beams are aligned at a fixed angle with respect to each other;when the scanning system is aimed at a region of interest (ROI) withinthe FOV, the plurality of light beams yield a dense resolution; and whenthe scanning system is aimed at a region of non-interest (RONI) withinthe FOV, the plurality of light beams yield a sparse resolution.
 24. Themethod of claim 23, wherein the dense resolution is an order ofmagnitude greater than the sparse resolution.
 25. The method of claim23, wherein the scanning system comprises a mirror and a polygon, themethod further comprising: coordinating a movement speed of the mirrorwith an aiming position of the scanning system within the FOV.
 26. Themethod of claim 25, further comprising: coordinating a repetition rateof the plurality of light beams with the aiming position of the scanningsystem within the FOV.
 27. The method of claim 25, further comprising:coordinating the movement speed of the mirror with a frame rate at whichthe scanning system operates such that lines of resolution within thesparse regions are distributed according to a predetermined pattern. 28.The method of claim 27, wherein the fixed angle, coupled with thecoordinated movement speed of the mirror, enables the lines ofresolution within the sparse regions to be distributed according to thepredetermined pattern.
 29. A method for using a light detection andranging (LiDAR) system, comprising: using the LiDAR system to scan afield of view (FOV), wherein the LiDAR system controls aim of at leastone light beam as it scans the FOV, the FOV bounded by a firstdirectional degree range and a second directional degree range; defininga range of interest (ROI) within the FOV that occupies a first portionof the first directional degree range; adjusting an angular resolutionof the at least one light beam while the LiDAR system scans the FOV,wherein when the at least one light beam is aimed at the ROI, theangular resolution is constant throughout the first portion of the firstdirectional degree range, and wherein when the at least one light beamis aimed at a region of non-interest (ROM), the angular resolution isvaried across the first directional degree range encompassing the RONI.30. The method of claim 29, wherein the adjusting the angular resolutioncomprises continuously adjusting the angular resolution as a function ofa degree within the first directional degree range of the RONI.
 31. Themethod of claim 29, wherein the adjusting the angular resolutioncomprises continuously adjusting the angular resolution such that adistance between light beam pulses is constant throughout the firstdirectional degree range of the RONI.
 32. The method of claim 29,wherein the adjusting the angular resolution comprises step-changeadjusting the angular resolution as a function of a degree within thefirst directional degree range of the RONI.
 33. The method of claim 29,wherein the scanning system comprises a movable mirror, wherein theconstant angular resolution is maintained by moving the movable mirrorat a constant speed, and wherein the varied angular resolution isachieved by moving the movable mirror at a variable speed.